Note: all pH measurements referenced in the below post are room temperature measurements.

In How to Brew, Palmer states that the goal is to hit a mash pH of between 5.4 and 5.8.

However, I've read a lot of posts on this forum where people state their target mash pH is 5.3. I've also read some posts where it has been posited that a mash pH higher than 5.6 can cause problems - regardless of the style of beer being brewed.

"A commonly accepted optimal range for mash pH is 5.2 - 5.7 with 5.5 being optimal for starch conversion activity but many authors report wort and beer quality benefits if the pH is lowered into the 5.2 - 5.4 range [Kunze, 2007][Narziss, 2005]. Kunze in particular lists the following benefits for a mash pH as low as 5.2. Since it is a good and fairly comprehensive list I cited it here. Some of these benefits listed will be explained in the following sections [Kunze, 2007]:"

I know a lot of people love John Palmer, but I think a lot of his advice is a bit off.

sierra nevada mashes at 5.2 from what i've read. i'll trust that they've done their homework on outcomes from hitting that number.

Is this at mash temp? That would be 5.4-5.5 at room temp, which is pretty typical. I think someone (Denny?) said they measure all pH at the intended use temperature when he was talking about their water adjustments. Please correct me if I made that up :-)

At any rate, the range for conversion is actually pretty large, so I don't think John is wrong. In practice, I think most brewers aim for the lower end of that range for other benefits.

I recently had a discussion on mash pH with alot of heavy hitters weighing in. All said that you measure mash pH at room temp. It is what the testing equipment (strips, probes)are calibrated for. The specific temperature might vary a few degrees based on the manufacturer, but still around what we all would consider room temp.I also recall saying that which end of the optimal range your mash pH falls in will result in a slightly different flavor profile. For me that is getting pretty granular so I just try to hit 5.2-5.7 at room temp.

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Michael P MitchemBeer and Ale Research Foundation (B.A.R.F.)AHA Member since 2011

I agree that you should cool your sample for the sake of your equipment. Unfortunately, it doesn't seem to be a reasonable assumption that all breweries and texts quote their readings at room temp. My impression of what Gordon said was the Sierra Nevada was either measuring or correcting their reading to be represented at mash temp. Perhaps he can add some more insight to this.

For a while now I'm trying to find a commercial brewing equipment manufacturer that offers in-line pH probes. The description for that probe may show how to convert between between mash and room temp measurements.

At least in my mind, and I have thought about this a lot) there is little doubt that pH measurements at room temp are standard practice. I'm curious though, if there are brewers in the industry that also have the ability to measure pH at process temp and how they correlate this with room temp pH measurements taken in the lab.